"A hate-fueled attack on a religious institution -- any religion -- is disgusting and appalling," Lamont said on Twitter.

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A hate-fueled attack on a religious institution -- any religion -- is disgusting and appalling. There is no place for it in our state or our nation. We will work w/ our local counterparts in #NewHaven to assist in the investigation and ensure those responsible are held accountable.

"Our hearts go out to all those who are affected," Marcano said, adding there's a $2,500 reward for any information leading to an arrest.

State police were also helping with the investigation Monday, "because it's a house of worship and what's going on in our nation right now," New Haven Fire Department Chief John Alston told WFSB.

"Any time a fire like this happens, it affects an entire community, not just families, but people of faith as well," Alston told the news station. "And we appreciate the well wishes. We've also spoken to the imam who is on the scene and we're going to provide as much assistance as we can."

He said the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives were also investigating.

ATF Special agents, who are certified fire investigators, went to the scene of the fire after the ATF offered technical assistance to the New Haven Police Department, who are the lead investigative agency, ATF Special Agent Matthew O'Shaughnessy told CNN.